Aki,
My friend and I bought fish without a broker last year. If your situation is the put-it-the back-of-the-trunk and drive home, then I wouldn't think you'd require a broker. But what the hell do I know. Anyhow, here's a copy of our secret map. It was many hours of work... good luck.
If you drive around yourselves, you might still need to borrow a pass to get into the mountains (earthquake related). Call Kaz Takeda in the evenings, at the New Otani around late March/early April. He's a US broker and will be doing a koi documentary -- he may be able to hook you up with a pass.
The 2006 KB thread about passes is here:
Yahoo! Maps Nagaoka/Ojiya - Mountain Passes
Thread with webcam/road conditions link:
Niigata Live Webcams
John